468 Miscellaneous. 



generally attributed. Considering the use that has been made of the 

 known physical forces for explaining the absorption of liquids from 

 the soil, the ascent of the sap, and also its descending course, I was 

 for a moment svirprised that no analogous experiment had been tried 

 in order to account for the absorption of the gases drawn from the 

 atmosphere. Nevertheless, this latter faculty of plants, which authors 

 have been content with indicating, is not less important than the 

 absorption of liquids by the roots. But it has not been capable of 

 explanation by the ordinary laws of physics. I am about to attempt 

 to prove that the aspiration by the roots, and the movements of 

 liquids in plants, cannot be effected under the influence of the phy- 

 sical forces to which such an important part is still ascribed, namely 

 capillarity and endosmose. Even those physiologists who ascribe a 

 great part in the ascent of the sap to capillarity, and especially to 

 endosmose, are compelled to admit that they are incapable of raising 

 liquids to the height of our trees, without the aid of the evaporation 

 which takes place in the leaves, and which, as they say, draws the 

 liquids towards those organs. For my part, I think, that if evapora- 

 tion causes the liquids to rise, it must prevent them from descending : 

 now they descend after rising ; therefore evaporation does not assist 

 in their elevation. I also think that Nature never makes use of 

 insufiicient causes like endosmose and capillarity ; and on the other 

 hand, the part attributed to endosmose is incompatible with the 

 constitution of plants. 



Suppose, for a moment, with the physiologists, that it is endosmose 

 which causes liquids to rise by the ligneous mass, and afterwards to 

 descend by the bark. In order that this phaenomenon should be 

 accomjdished, the density of the juices must constantly increase as 

 they rise (this is what has been observed) ; and this density must 

 also increase in passing through the leaves from the ligneous mass to 

 the bark, and in descending from cell to cell in the interior of the 

 cortical tissue. (At the last meeting of the xlcademy I stated that 

 these juices do not descend in the laticiferous vessels, which have 

 other functions.) We could not, moreover, recur exclusively to 

 gravitation, seeing that there are pendent branches as well as erect 

 ones. 



The botanists who admit the endosmotic theory have not remarked 

 that they have thus, side by side, two currents of liquids of different 

 densities ; they have not noticed that the ascending sap, being less 

 dense than the descending, would necessarily be attracted by the 

 latter, as the membranes are permeable ; they have not considered 

 that throughout the whole length of the trunk there would neces- 

 sarily be a horizontal, centrifugal current, until an equilibrium of 

 density was established, and that then the double ascending and 

 descending current could not exist. As this is not the case, the 

 endosmotic theory is erroneous. A force distinct from endosmose 

 must therefore preside over the absorption of the liquids drawn from 

 the soil, as well as over that of the gases taken from the atmosphere. 

 And thus there are in plants other movements than that of the 

 ascending and descending sap. This sap, in its course, gives off, into 



